Humboldt H-2783 Pressure Meter - Manual (Page 5)

5. Close both petcocks and immediately press down on the thumb le-
ver exhausting air into the base. Wait a few seconds until the hand is
stabilized. If all of the air was eliminated and the initial pressure line
was correctly selected, the gauge should read zero. If two or more
tests show a consistent variation from +/- 0.1% in the result, then
change the initial pressure line to compensate for the variation. Use
the newly established initial pressure line for subsequent tests.
6. Screw the supplied curved tube into the outer end of the petcock
and by pressing on the thumb lever and controlling flow with the
petcock lever. Fill the supplied 5% calibrating vessel (354ml) level
full of water from the base.
7. Release the air at the free petcock. Open the other petcock and let
the water in the curved pipe run back into the base. There is now 5%
air in the base.
8. With both petcocks open, pump air pressure in the exact manner as
outlined in step
4. Close the petcocks and immediately press the thumb lever. Wait a
few seconds for exhaust air to warm to normal temperature and for
the needle to stabilize. The dial should now read 5%.
9. If two or more consistent tests show that the gauge reads incorrectly
at 5% air in excess of +/- 0.1% (or whatever is considered satisfac-
tory), then remove the gauge glass and reset the dial hand to 5% by
turning the calibration screw located on the indicating pointer.
10. When the gauge hand reads correctly at 5%, additional water may
be withdrawn in the same manner to check results at 10%, 15%,
20%, etc.
Maintenance Tips
1. Prompt cleaning with water of the air meter cover and pot, both
inside and out will ensure a proper seal and volume are maintained.
2. Periodic oiling of petcock screws will prevent them from seizing.
WD-40 or a similar product is sufficient.
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